All you would really need is a DAP-2553 http://www.dlink.ca/products/?sec=2&pid=697
Maybe any access point will suffice. I'm not sure about the lower end models, but the 2553 acts as a client, AP and DWS/AP
so for example, you could wire your gaming consoles to the DAP, set the dap as a client, which acts as a wireless network adapter for all your devices. The DAP then will wirelessly connect to the dir 655, which the dir 655 is wired to the other computers upstairs. Meanwhile any other computers upstairs can still have wireless access by connecting to the dir 655. So unlike the diagram you posted, which is completely unecessary, just a way for dlink to make more money than is needed, you only need 2 devices. You may only need what you have but you are going to need one long cord to connect the dir to your other router's.
BTW, if you do decide to buy it, DONT buy it from the dlink shop. They want nearly 500.00 for it. You can get it for about 140.00 US from tiger direct.com. tigerdirect.ca doesn't offer it.
I think it's a worth while investment. It is certainly one that I am thinking about getting.